The present invention relates a radio paging receiver and, more particularly to a paging receiver having an oscillator circuit of low power consumption.
A paging receiver such as the one disclosed in the U.S. Pat. Nos. 4,181,893 or 4,160,240 is required to have low power consumption as well as a small size and multiple or complicated functions (for example, display, alert and battery saving functions). To meet this requirement, a most recently developed pager such as the one disclosed in the U.S. Pat. No. 4,196,310 is equipped with a microprocessor, which permits various complicated functions and flexibility.
Such pagers require a variety of timing signals to provide the desired multiple functions.
While these signals are produced by frequency-dividing the output of an oscillator having a frequency in the order of tens of KHz, the alert tone is also produced by the same process. If a quartz oscillator at a frequency around 30 KHz is used for this purpose, it takes a long time, say several seconds, to reach a stable state after switch-on, because of its high equivalent resistance. This presents a problem in connection with the testing function of a radio paging receiver, such as a pocket bell as it is called in Japan. Depression of the switch for testing will not immediately result in the alert tone sounding, thus failing to indicate that the receiver is ready. Therefore, with this type of paging receivers wherein power is not supplied to its oscillator until its power switch is turned on the user must be informed before hand that there is a time lag in the response to testing.
Furthermore, even after oscillation is started, the sound produced is not normal and in some cases is offensive to the ear until the oscillation frequency is stabilized.
To overcome this problem, a proposal has been made in U.S. Pat. No. 4,195,263 assigned to the same assignee as the present application. In the receiver disclosed in the referenced patent, the battery is directly connected to the oscillator circuit, which accordingly always stays on. This makes it possible for the receiver to produce a normal frequency tone in response to the power switch for the whole of the receiver being turned on.
However, the teaching of this prior art is only applicable to the situation where no more than one power source is used.
Generally, a receiver to be equipped with a CMOS microprocessor or circuit requires a 3-volt (3 V) power source for operation, in addition to a one-volt (1 V) power source for the aforementioned purpose of keeping the oscillator circuit alive. In other words, at least two power sources are needed for such a paging receiver. As a result, the teaching of the above-referenced patent is not directly applicable to a paging receiver of this type.